This project is a study of the regulatory responses made by the tissues to changes in amino acid supply from the diet. The research program initially focused on parallel changes in protein, RNA and phospholipid content of the liver resulting from changes in the protein content of diet, and progresses to a study of short-term changes in cell metabolism caused by alterations in amino acid supply and eventually developed in integrated picture of these responses. The current research period will advance this in the following ways: (a) In the field of ferritin synthesis and its control, we shall continue to explore the structure and assembly of the ferritin shell, the mechanism of insertion of sugar residues, and the control by iron administration. (b) The role of mRNP particles will be further studied as regulators of protein synthesis. The function of the protein of mRNP will be explored further. A cDNA probe will be prepared and used to explore mRNP particles for ferritin message, and the effects of iron on this. (c) Placental extracts will continue to be studied for evidence of peptide hormones analogous to TSH, VIP, etc., and also LHRH as a potential control for HCG secretion. (d) A rat model for the effects of protein deficiency on placental peptide hormone secretion will be examined further. The theory that the lactogenic hormone of rat placenta acts on the maternal organism by stimulating somatomedin secretion from liver will be tested.